Noninvasive blood analyzer

ABSTRACT

A noninvasive blood analyzer is provided which comprises: a light source for illuminating a part of tissues of a living body including a blood vessel; an image pickup section for picking up an image of the illuminated blood vessel and tissues; and an analyzing section for analyzing the picked image; the analyzing section including an extracting section for extracting image density distribution across the blood vessel in the image as an image density profile, a quantifying section for quantifying configurational characteristics of the image density profile, a computing section for computing the concentration of a blood constituent on the basis of the quantified characteristics, and an outputting section for outputting a computation result. The blood analyzer can measure the concentration of blood hemoglobin and the hematocrit in real time with an improved repeatability without blood sampling.

This application is the national phase under 35 U.S.C. 371 of prior PCTInternational Application No. PCT/JP96/03894 which has an Internationalfiling date of Dec. 27, 1996 which designated the United States ofAmerica, the entire contents of which are hereby incorporated byreference.

DESCRIPTION

1. Technical Field

The present invention relates to a noninvasive blood analyzer. Theanalyzer of the present invention is capable of transcutaneouslymonitoring an amount of a blood constituent such as hemoglobinconcentration or hematcrit in real time with an improved repeatabilitywithout sampling blood from a living body.

2. Background Art

The hematology test of blood in a peripheral blood vessel is one of themost important and frequently performed tests in the clinicalexamination. Particularly, test items essential for the diagnosis on thecase of anemia are hemoglobin concentration and hematocrit. Thehematology test currently performed requires blood sampling frompatients. However, the frequent blood sampling imposes a burden onpatients and creates a risk of infection due to accidental sticking withan injection needle.

In view of the foregoing, there have been proposed apparatuses fortranscutaneous (noninvasive) measurement on the aforesaid test items.For example, Japanese Examined Patent Publication No. HEI- 3-71135discloses a hemoglobin concentration measurement apparatus for measuringblood hemoglobin on the basis of a change in the light intensity due topulsation of light of a plurality of wavelengths projected onto a livingbody. Similarly, U.S. Pat. No. 5,372,136 discloses a system and methodfor determining hematocrit in blood by utilizing pulsation and the like.

However, a problem associated with the accuracy accompanies these artsfor determining an absolute value, because the volume of the blood to bea test subject is not determined. Further, it is predicted that themeasurements may vary depending on the body part to which the sensor isattached, resulting in a poor repeatability.

U.S. Pat. No. 4,998,533 discloses an apparatus for performingmeasurement on the aforesaid test categories on the basis of an image ofa blood stream in blood capillary, which however, requires a large-scaleconstruction. Although it has been reported that a transmitted lightimage of blood vessels in a part of a living body such as a finger canbe obtained, no attempt has been made to perform a quantitative analysison the aforesaid test items by analyzing the transmitted light image.

DISCLOSURE OF THE INVENTION

In view of the foregoing, the present invention provides an apparatusand method which are adapted to obtain a transmitted light image of ablood vessel in tissues of a living body such as a finger and analyzethe transmitted light image with a simplified construction forperforming measurement on the aforesaid test items with an improvedrepeatability.

More specifically, when light is allowed to pass through body tissuesincluding a blood vessel and a transmitted light image is picked up, ablood vessel portion of the image is dark because of light absorption byblood constituent contained in blood, and the other image portion isbright because the other part of the body tissues transmits the light.In accordance with the present invention, the concentration of a bloodconstituent (e.g., hemoglobin) is quantified by a comparison of imagedensities and, when required, the determined concentration is correctedon the basis of the depth at which the blood vessel is present.

In accordance with the present invention, there is provided anoninvasive blood analyzer which comprises: a light source forilluminating a part of tissues of a living body including a bloodvessel; an image pickup section for picking up an image of theilluminated blood vessel and tissues; and an analyzing section foranalyzing the picked image; the analyzing section analyzing imagedensity of the blood vessel in the picked image to compute an amount ofa blood constituent and output a compution result.

In the present invention, the living body is meant by mammals includinghuman, and the part of the tissues of the living body is meant by a partof tissues as they are in the living body, e.g., a finger or earlobe,but not meant by tissues separated from the living body.

In the analyzer of the present invention, the analyzing section mayinclude an extracting section for extracting image density distributionacross the blood vessel in the picked image as an image density profile,a quantifying section for quantifying configurational characteristics ofthe image density profile, a computing section for computing the amountof the blood constituent on the basis of the quantified characteristics,and an outputting section for outputting a computation result.

The analyzer of the present invention preferably further includes afixing member for fixing the light source and the image pickup sectionrelative to the part of the living body to allow the image pickupsection to pick up an image of a desired portion of the tissues of theliving body.

In the present invention, the picked image may be either a transmittedlight image or a reflected light image.

Usable as the light source in the present invention are a semiconductorlaser (hereinafter referred to as "LD"), an LED and a halogen lightsource. The part of the living body may be illuminated with the lightdirectly or via an optical fiber. The wavelength of the light ispreferably within a range between 400 and 950 nm, at which the lightpasses through the body tissues and the light absorption by water is notgreat. For example, a range between 600 and 950 nm is used for thetransmitted light image while a range between 400 and 950 nm is used forthe reflected light image.

More preferably, the light source is preferably comprised of a lightemitting device which is adapted to selectively emit light beams offirst and second wavelengths or light beams of three or morewavelengths. It is desirable that the first and second wavelengths aresubstantially isosbestic for oxidized and reduced hemoglobins.

Two or more wavelengths are required for the determination of an amountof a blood constituent, that is, hemoglobin concentration andhematocrit. If it is simply desired to monitor anemia condition, onlyone wavelength may be used.

The image pickup section may be comprised of an optical system includinga lens and an image pickup device such as a CCD.

Since the image pickup section is simply adapted to take an imagedensity profile across the blood vessel, a line sensor or a photodiodearray may be used as the image pickup device instead of the CCD. Theimage density profile is preferably taken along a line perpendicular tothe blood vessel.

Alternatively, the image density profile may be taken by moving a singlephotodiode in a direction across the blood vessel.

The optical system of the image pickup section can be constructed with aTV lens (e.g., BD1214D available from COSMICAR Inc.) alone.

Alternatively, the optical system of the image pickup section may becomprised of a pair of lenses having the same numerical aperture or thesame focal distance and effective lens diameter, the pair of lensesrespectively serving as an object lens and a focusing lens which aredisposed along the same optical axis such that the front focal point ofone lens coincides with the rear focal point of the other lens, andbetween which an optical space filter having two-dimensionally differenttransmittances is disposed (such an optical system is hereinafterreferred to as "conjugate optical system"). The space filter herein usedhas a variation in the two-dimensional transmittance distribution.Usable as the space filter are a light blocking plate having a pin holeor an annular slit, and a liquid crystal shutter designed such that thetransmittance distribution thereof can be changed by an electric signal.

The analyzing section includes the extracting section, the quantifyingsection, the computing section and the outputting section, and isadapted to compute on the basis of the obtained image density profilefor determination of the amount of a blood constituent such ashemoglobin concentration, hematocrit or anemia condition and output thecomputation result. Usable for the analyzing section is a commerciallyavailable personal computer.

The extracting section of the analyzing section extracts image densitydistribution across the blood vessel as an image density profile fromthe picked image.

The quantifying section may normalize the extracted image densityprofile and compute a peak value h of the normalized image densityprofile.

Further, the quantifying section may determine a distribution width wcorresponding to the diameter of the blood vessel in the image densityprofile and correct the peak value h on the basis of the distributionwidth w.

Where images of the same part of the tissues of the living body arepicked up at the first and second wavelengths to afford first and secondprofiles respectively having peak values h1 and h2 and distributionwidths w1 and w2, the quantifying section estimates the subcutaneousdepth L of the blood vessel on the basis of the ratio between thedistribution widths w1 and w2, and corrects the peak values h1 and h2.Thus, the computing section can compute the hemoglobin concentration andthe hematocrit on the basis of the corrected peak values.

Where the conjugate optical system employs a light blocking plate havingan annular slit as the space filter, the incident angle of light fromthe body tissues to the object lens is determined by the configuration(diameter or slit width) of the annular slit so that only the lightentering at a predetermined incident angle serves to form a scatterlight image of the blood vessel. The scatter light image reflects aninfluence of the disturbance of a blood vessel image by the bodytissues. Therefore, by picking up scatter light images at a plurality ofdifferent scattering angles by changing the diameter of the annularslit, the quantifying section can quantify the influence of the bodytissues to correct the detected concentration of the blood constituentmore accurately.

In this case, since the scatter light image varies sensitively dependingon the condition of the focusing on the blood vessel, the in-focusposition can distinctly be detected by scanning the focal point of theimage pickup section (object lens) from the surface of the body tissueto a deeper position, thereby allowing the quantifying section todirectly determine the depth at which the blood vessel is present.Therefore, the aforesaid computation data can be corrected on the basisof the depth thus determined.

More specifically, a series of scatter light images of the blood vesselare obtained at a predetermined light incident angle by moving the focalpoint from the surface of the body tissues to the deeper position. Then,the quantifying section directly determines the depth L of the bloodvessel on the basis of the position of the focal point at which thesharpest one of the series of the scatter light images is obtained, andthe peak values h1 and h2 are corrected on the basis of the depth L.

Further, the quantifying section determines scatter absorptioncharacteristics of the body tissues on the basis of a plurality ofdifferent scatter light images obtained at that focal point position bytwo-dimensionally varying the transmittance of the optical filter, andthen corrects the peak values h1 and h2 and the distribution widths w1and w2 on the basis of the scatter absorption characteristics.

The computing section computes the amount of the blood constituent suchas hemoglobin concentration and hematocrit on the basis of thequantified configurational characteristics of the image densityprofiles. Here, hematocrit means a volume ratio of erythrocytes toblood. Usable as the outputting section are a CRT, an LCD and the like.

In accordance with another aspect of the present invention, there isprovided a noninvasive blood analyzing process which comprises the stepsof: illuminating a part of tissues of a living body including a bloodvessel; picking up an image of the illuminated body tissues; andanalyzing the picked image; the analyzing step including the steps ofextracting image density distribution across the blood vessel in thepicked image as an image density profile, quantifying configurationalcharacteristics of the image density profile, computing an amount of ablood constituent on the basis of the quantified characteristics, andoutputting a computation result.

Also, in accordance with the present invention, it can provide thenoninvasive blood analyzing process further comprising the steps of:allowing an optical system to receive light from the body tissues at apredetermined incident angle with respect to an optical axis of theoptical system and obtaining a series of scatter light images of theblood vessel by moving a focal point of the optical system from thesurface of the body tissues to a deeper position; detecting the depth ofthe blood vessel on the basis of the position of the focal point atwhich the sharpest one of the series of the scatter light images isobtained; determining scatter/absorption characteristics of the bodytissues on the basis of a plurality of scatter light images obtained atthat focal point position by changing the incident light angle; andcorrecting the characteristics of the profile on the basis of thescatter/absorption characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the construction of a bloodanalyzer according to Embodiment 1 of the present invention;

FIG. 2 is a perspective view illustrating the appearance of the bloodanalyzer of Embodiment 1 of the present invention;

FIG. 3 is a sectional view illustrating a major portion of the bloodanalyzer of Embodiment 1 of the present invention;

FIG. 4 is a flow chart for explaining the operation of the bloodanalyzer of Embodiment 1 of the present invention;

FIG. 5 is a photograph of an image (a gray scale image displayed on aCRT) picked by the blood analyzer of Embodiment 1 of the presentinvention;

FIG. 6 is a graphical representation for explaining an image densityprofile obtained by the blood analyzer of Embodiment 1 of the presentinvention;

FIG. 7 is a graphical representation for explaining an image densityprofile normalized in the blood analyzer of Embodiment 1 of the presentinvention;

FIG. 8 is a front view of a light source of the blood analyzer ofEmbodiment 1 of the present invention;

FIG. 9 is a diagram for explaining an exemplary display of the bloodanalyzer of Embodiment 1 of the present invention;

FIG. 10 is a block diagram illustrating the construction of a bloodanalyzer according to Embodiment 2 of the present invention;

FIG. 11 is a sectional view illustrating major portions of the bloodanalyzer of Embodiment 2 of the present invention;

FIG. 12 is a sectional view taken along a line X--X in FIG. 11;

FIG. 13 is a flow chart illustrating the operation of the blood analyzerof Embodiment 2 of the present invention;

FIG. 14 is a flow chart illustrating the operation of the blood analyzerof Embodiment 2 of the present invention;

FIG. 15 is a flow chart illustrating the operation of the blood analyzerof Embodiment 2 of the present invention;

FIG. 16 is a photograph of an image (a gray scale image displayed on aCRT) picked by the blood analyzer of Embodiment 2 of the presentinvention;

FIG. 17 is a graphical representation for explaining an image densityprofile obtained by the blood analyzer of Embodiment 2 of the presentinvention;

FIG. 18 is a graphical representation for explaining an image densityprofile normalized in the blood analyzer of Embodiment 2 of the presentinvention;

FIG. 19 is a graphical representation for explaining the position of afocal point and the width of scatter distribution detected by the bloodanalyzer of Embodiment 2 of the present invention; and

FIG. 20 is a photograph illustrating a comparative example with respectto FIG. 16.

FIG. 21 is a sectional view showing a structure of a detecting sectionaccording to Embodiment 3 of the present invention.

FIG. 22 is a bottom view of the detecting section.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will hereinafter be described in detail by way ofthree embodiments. It should be noted that these embodiments are notlimitative of the invention.

Embodiment 1

There will first be described the construction of a blood analyzeraccording to Embodiment 1 of the present invention.

FIG. 1 is a block diagram illustrating the construction of the bloodanalyzer. As shown, in a detecting section 1, it includes a light source11 for illuminating a part of tissues of a living body including a bloodvessel and an image pickup section 12 for picking up a transmitted lightimage of the illuminated blood vessel and tissues.

An analyzing section 2 includes an extracting section 21 for extractingimage density distribution taken along a line perpendicular to the bloodvessel in the image picked by the image pickup section 12 as an imagedensity profile, a quantifying section 22 for quantifying theconfigurational characteristics of the extracted image density profile,a computing section 23 for computing the amount of a blood constituenton the basis of the quantified characteristics, and an outputtingsection (CRT) 24 for outputting a computation result. The analyzingsection 2 may be comprised of a personal computer.

FIG. 2 is a perspective view of the analyzer shown in FIG. 1. The lightsource 11 and the image pickup section 12 incorporated in the detectingsection 1 are connected to the analyzing section 2 through signal cables3.

FIG. 3 is a sectional view of the detecting section 1. The detectingsection 1 includes the light source 11, and the image pickup section 12having a lens 14 and an image pickup device 15. When a finger 16 isinserted into an open cavity 13, the light source 11 illuminates thefinger 16 and an transmitted light image is picked up by the imagepickup device 15 via the lens 14. The open cavity 13 gradually decreasestoward the innermost position at which the finger tip is located, sothat the inserted finger 16 is loosely fitted therein, therebyconstituting a fixing member.

The image pickup device 15 is comprised of a CCD. FIG. 8 is a front viewof the light source 11, which includes LEDs 11a and 11b.

In this embodiment, the LED 11a employs VSF665M1 (available from OPTRANSCo.) having a center wavelength of 660 nm and a half value width 40 nmand the LED 11b employs L2656 (available from Hamamatsu Photonics Co.)having a center wavelength of 890 nm and a half value width 50 nm.

An analyzing process to be performed by the analyzing section 2 of theblood analyzer having such a construction will be described withreference to a flow chart shown in FIG. 4.

(1) Computation of Hemoglobin Concentration and Hematocrit

When the finger is illuminated at a wavelength offered by the LED 11a(hereinafter be referred as "first wavelength") (Step 1) and atransmitted light image is picked up, an image of a blood vessel (vein)located near the skin on the side of the CCD 15 is obtained as shown inFIG. 5. Where the blood vessel of interest has a diameter of about 1 mm,quantitative results can be obtained with an improved repeatability.

In this case, where a highly coherent LD is used as the light source, animage free from speckles as shown in FIG. 5 can be obtained because thelight is scattered by the tissues. In turn, an area in the image wherethe blood vessel stands in the sharpest contrast is searched for (Step1a), and enclosed in a quadrilateral configuration as shown in FIG. 5,which is employed as an analytic area (Step 2).

Thus, a blood vessel at substantially a constant subcutaneous depth canbe analyzed.

An image density profile (FIG. 6) along a line perpendicular to theblood vessel in this area is obtained (Step 3).

Then, the image density profile is normalized by a base line. The baseline is determined on the basis of a portion of the image densityprofile corresponding to the tissues other than the blood vessel by theleast square method. Thus, the image density profile of FIG. 6 isnormalized as shown in FIG. 7 (Step 4).

The image density profile thus obtained is independent of the amount ofincident light. A peak height h1 and a half value width (distributionwidth at a height of (1/2)h1) w1 are determined from the normalizedimage density profile (FIG. 7)(Step 5).

The peak height h1 thus obtained is indicative of the ratio of the imagedensity of the blood vessel (i.e., a portion where blood is present) tothe image density of the other portion where blood is absent. Theparameter corresponding to a parameter which is obtained by theavascularization method (which is adapted to analyze blood on the basisof the ratio of the image density obtained when the blood is present tothe image density obtained when the blood is avascularized) or by thepulsatile spectrometry (which is adapted to obtain signal components insynchronization with the pulsation of a blood flow and extract a signalcomponent indicative of the pulsated blood flow for blood analysis,i.e., on the basis of the principle of a pulse oxymeter) can bedetermined without the utilization of the pulsation or theavascularization.

More specifically, the scatter factor S1 and absorption factor factor A1of the blood at the first wavelength, if conforming to the Beer Law, isexpressed as follows:

    log(1-h1)=-k(S1+A1)w1                                      (1)

wherein k is a proportional constant.

It is considered that the scatter factor S1 and the absorption A1 aredirectly proportional to the hematocrit HCT and the hemoglobinconcentration HGB as follows:

    S1=σ1HCT, A1=σ2HGB (2)

Therefore,

    log(1-h1)=-(kσ1HCT+kσ2HGB).circle-solid.w1                                                    (3)

The aforesaid process sequence is performed by employing a wavelengthoffered by the LED 11b (hereinafter referred to as "second wavelength")for determination of a peak height h2 and a distribution width w2 (Steps6 to 10).

Similarly, the scatter factor S2 and the absorption factor A2 aredetermined as follows:

    log(1-h2)=-k(S2+A2)w2=-(kσ3HCT+kσ4.circle-solid.HGB)w2                          (4)

Since the constants k, σ1, σ2, σ3 and σ4 are experimentally determined,the HGB and the HCT are determined by h1, h2, w1 and w2.

In reality, the image is blurred by tissues intervening between theblood vessel and the detecting section and, hence, the observed peakvalues are smaller than the case where there are no intervening tissues.Therefore, the relation of the aforesaid factors are expressed asfollows:

    log(1-h)=-k(S+A)w+T                                        (5)

wherein S is the scatter factor of the blood, A is the absorption factorof the blood, and T is a factor which indicates the influence of theblurring and is a function of the thickness L of the tissues (or thedepth at which the blood vessel is located; hereinafter referred tosimply as "depth").

It has been experimentally found that the factor T can be kept virtuallyconstant by properly selecting a measuring area such that the bloodvessel image in the obtained image stands in the sharpest contrast.Therefore, no practical problem arises if the factor T is regarded as aconstant for application to an anemia checker.

(2) Correction of Computed Hemoglobin Concentration and Hematocrit

To improve the accuracy of the computation of the hemoglobinconcentration and the hematocrit, the correction is made as follows.

When the analytic area is defined in the same area as defined by usingthe first wavelength, the half value widths w1 and w2 are equal to eachother if the influence of the blurring is negligible. However, adifference between the half value widths w1 and w2 increases as theinfluence of the blurring increases (the half value width increases withthe increase in the degree of the blurring).

Therefore, the depth L can be determined on the basis of the ratiobetween the half value widths w1 and w2 from the following equation(Step 11).

    L=f(w2/w1)                                                 (6)

wherein f is a function to be experimentally determined.

The peak heights h1 and h2 and the half value width w1 are corrected onthe basis of the depth L by the following equation for determination ofcorrected values H1, H2 and W (Step 12).

    H1=g1(h1,L)                                                (7)

    H2=g2(h2,L)                                                (8)

    W=g3(w1,L)                                                 (9)

wherein g1, g2 and g3 are functions to be experimentally determined.

The hemoglobin concentration HGB and the hematocrit HCT are computed inthe aforesaid manner on the basis of the corrected values H1, H2 and W(Step 13).

In the analyzing section 2, the extracting section 21 implements Steps2, 3, 7 and 8, the quantifying section 22 implements Step 4, 5, 9 and10, and the computing section 23 implements Steps 11 to 14.

The results thus obtained are displayed in the outputting section (CRT)24 as shown in FIG. 9.

In FIG. 9, images D1, D2 and D3 correspond to FIGS. 5, 6 and 7,respectively. "LED1" and "LED2" correspond to the LED 11a and LED 11b,respectively. "PEAK" and "WIDTH" correspond to the peak heights h1, h2and the half value widths w1, w2, respectively.

Although the image pickup device 15 is comprised of the CCD in thisembodiment, a line sensor may be employed instead. In such a case, thedensity profiles can directly be obtained in Steps 3 and 8 shown in FIG.4. However, a special consideration is required, e.g., a line sensorhaving two line elements should be employed, because the line sensor isnot always disposed perpendicular to the blood vessel.

While the computation of the hemoglobin concentration and the hematocrithas been described above, the analyzer according to this embodiment canalso be used as an anemia checker. Since the hemoglobin concentrationand the hematocrit are correlated with each other, the rough check ofthe degree of the anemia (anemia check) can be performed by implementingpart of the process sequence (Steps 1 to 5) in FIG. 4 by using eitherone of the first and second wavelengths.

Further, where a blood vessel at a constant depth is of interest, thestep for the depth correction can be omitted. Rough depth correction canbe achieved by searching for an image area having the sharpest contrastas in Step 1a of FIG. 4.

Embodiment 2

There will first be described the construction of a blood analyzeraccording to Embodiment 2 of the present invention.

In this embodiment, the image pickup section 12 and the analyzingsection 2 are modified for more precise correction than the correctionprocess in Embodiment 1.

FIG. 10 is a block diagram illustrating the construction of the analyzerof Embodiment 2, in which like reference numerals denote like parts inFIG. 1. A detecting section 1a includes a light source 11 forilluminating part of tissues of a living body including a blood vessel,and an image pickup section 12a having a conjugate optical system.

FIG. 11 is a sectional view of the detecting section 1a. The lightsource 11 has the same construction as in Embodiment 1 and, therefore,an explanation thereto is omitted.

The image pickup section 12a includes a driving stage 19a movable indirections of arrows A and B and incorporating an object lens 14a and afocusing lens 14b each having the same numerical aperture, an imagepickup device 15, a space filter 18 and a filter driving section 19b,and a mirror 17.

The rear focal point of the lens 14a coincides with the front focalpoint of the lens 14b. That is, the lenses 14a and 14b are disposed soas to have a common focal point, at which the space filter 18 isdisposed. The image pickup device 15 is disposed at the rear focal pointof the lens 14b. Like in Embodiment 1, a CCD or the like is employed asthe image pickup device 15.

As shown in FIG. 11, the stage 19a is mounted on a sliding mechanism 31,which is moved in the directions of the arrows A and B by driving astepping motor M1 to be. Thus, the position of the focal point F of thelens 14a can be adjusted.

FIG. 12 is a sectional view taken along a line X--X in FIG. 11. Thefilter driving section 19b has a sliding section 34 which supports afilter attachment plate 33 slidably in directions of arrows C and D.Since a pinion 33b of the stepping motor M2 engages a rack 33 providedin the upper portion of the filter attachment plate 33, the filterattachment plate 33 travels in the directions of the arrows C and D whenthe stepping motor M2 is driven.

Space filters 18, 18a, 18b and 18c are attached to the filter attachmentplate 33. The space filters 18, 18a and 18b are light blocking platesrespectively including annular light transmission slits 32, 32a and 32bhaving different diameters. The space filter 18c is a light blockingplate having a round light transmission window 32c.

Therefore, any selected one of the space filters 18, 18a, 18b and 18ccan be placed at the common focal point by means of the filter drivingsection 19b. A situation where virtually no filter is placed can becreated by placing the space filter 18c at the common focal point.

The analyzing section 2b includes an extracting section 21 forextracting a profile from the picked image, a quantifying section 22 forquantifying the profile, a computing section 23 for computing thehemoglobin concentration and the hematocrit on the basis of parametersthus quantified, an outputting section (CRT) 24 for displayingcomputation results, and a controlling section 25 for driving thestepping motors M1 and M2 to control the position of the focal point andthe insertion of the space filters.

In the detecting section la, as shown in FIG. 11, light emitted from thelight source 11 is allowed to pass through a finger 16, then turned by90β by means of the mirror 17, and focused on the image pickup device 15via the lenses 14a and 14b.

Where the space filter 18 (FIG. 12) is located at the position of thecommon focal point, only light scattered at a particular angle bytissues of the finger 13 is focused on the image pickup device 15. Theparticular angle is determined by the diameter of the slit 32.

Further, by moving the stage 19a along the optical axis (in thedirection of the arrow A or B), the focal point F can be located at adesired position in the tissues of the finger 16.

An analyzing process to be performed by the analyzing section 2b of theblood analyzer having such a construction will be described withreference to a flow chart shown in FIG. 13.

(1) Computation of Hemoglobin Concentration and Hematocrit

First, the space filter 18 is removed from the position of the commonfocal point by the filter driving means 19b (Step S0). Thus, the imagepickup section has substantially the same construction as the imagepickup section in Embodiment 1. Since the process for computing thehemoglobin concentration and the hematocrit which is performed inaccordance with subsequent steps 1a to 10 is the same as in Embodiment 1shown in FIG. 4, an explanation thereto is omitted.

(2) Correction of Computed Hemoglobin Concentration and Hematocrit

Since this embodiment is characterized by a correction process in Step12a, the correction process will hereinafter be described in greaterdetail with reference to flow charts shown in FIGS. 14 and 15.

The space filter 18 is set at the position of the common focal point bymeans of the filter driving section 19b (Step 21).

In this state, the focal point F is located on the skin surface of thefinger (Step 23). The initial position of the focal point F ispredetermined because the finger insertion position is preliminarilyfixed.

Then, an image is picked up (Step 24).

The image pickup step is different from Step 1 (FIG. 4). That is, thepicked image is formed from light scattered within that particularangle, and hereinafter referred to as "scatter image" for avoidance ofconfusion.

The scatter image is shown in FIG. 16. It should be noted that, sincethe scatter image is formed from the scatter light alone, onlyperipheral portions of the blood vessel in the scatter image have a highbrightness. For reference, an image of the same object obtained in Step1 of FIG. 4 is shown in FIG. 20.

In the extracting section 21, a profile within the analytic area definedin Step 2 (FIG. 4) is obtained from the scatter image (Step 25). Thisprofile is referred to as "scatter profile" for discrimination thereoffrom the image density profile obtained in Step 3 (FIG. 4). An exemplaryscatter profile is shown in FIG. 17.

Further, the quantifying section 22 determines a base line BL of thescatter profile, and then a peak height sh and a distribution width swof the scatter profile are determined as shown in FIG. 18 (Step 26).

The peak height and the distribution width will hereinafter be referredto as "scatter peak height SH" and "scatter distribution width SW",respectively, for avoidance of confusion. A value of the scatterdistribution width SW thus determined is once stored as the minimumvalue (Step 27).

In turn, the focal point F is moved by a predetermined distance ΔFinwardly of the finger 13 (Step 28).

The distance ΔF is of the order of 0.1 mm.

In this state, the process sequence of Steps 24 to 26 is repeated fordetermination of the scatter peak height sh and the scatter distributionwidth sw.

The scatter distribution width sw thus determined is compared with theminimum value previously stored. If the scatter distribution width sw issmaller than the stored value, the scatter distribution width isemployed as a new minimum value (Step 27).

The process sequence of Steps 24 to 27 is repeated until the focal pointreaches a predetermined depth (Step 28).

The predetermined depth may be about 2 mm, since the blood vessel ofinterest is typically located at a subcutaneous depth of 1 to 2 mm.

The scatter peak widths SW thus obtained are plotted with respect to theposition of the focal point as shown in FIG. 19. The scatter peak widthis the minimum when the focal point is located at the depth at which theblood vessel is present. This means that, when the focal point of theimage pickup system coincides with the position of the blood vessel ofinterest, the scatter light image is the sharpest.

Therefore, the position of the focal point which AAA offers a bloodvessel image having the minimum width corresponds to the subcutaneousdepth L' of the blood vessel described in Embodiment 1 (Step 29). Thatis, the subcutaneous depth can be determined more accurately. A scatterpeak height SH1 and a scatter distribution width SW1 are obtained inthis state (Step 30).

In accordance with this flow chart, only the minimum value of thescatter distribution width is stored. Alternatively, all the scatterpeak heights SH and scatter distribution width SW obtained by changingthe position of the focal point are stored, and then fitted to anappropriate function for determination of the minimum value.

In turn, the focal point of the image pickup system is moved to thesubcutaneous depth L' (Step 31), and then the space filter currentlyemployed is replaced with the space filter 18a is attached by means ofthe filter driving section 19b.

The space filter 18a is different in the diameter from the space filter18. This means that the angle range of the scatter light for the imageformation is changed.

A scatter light image is picked up with the use of the space filter 18a(Step 33), and the extraction (Step 34) and quantification (Step 35) ofa scatter profile are carried out in the same manner as described above.Then, a scatter peak height SH2 and a scatter distribution width SW2 aredetermined (Step 36). Further, substantially the same process sequenceas described above is performed with the use of the space filter 18b(steps 37 to 41).

The scatter peak heights SH1 to SH3 and the scatter distribution widthsSW1 to SW3 thus obtained reflect the optical characteristics, i.e., thescatter factor and absorption factor of the tissues of the living body.More specifically, the scatter peak height decreases, as the absorptionfactor of the living body becomes higher. The scatter peak heightdecreases and the scatter distribution width increases, as the scatterfactor becomes higher. Therefore, these parameters reflect the scatterfactor and absorption factor of the tissues of the living body.

As described in Embodiment 1, the image density profile is influenced bythe disturbance by the body tissues. The correction for the disturbanceis carried out on the basis of the ratio between the distribution widthsof the image density profiles in Embodiment 1.

In Embodiment 2, since the disturbance by the body tissues can directlybe quantified on the basis of the aforesaid parameters, more accurateresults can be obtained. More specifically, the peak height h1 and thedistribution width w1 in the equation (4) are corrected by the followingequation for determination of a corrected peak height H1 and a correcteddistribution width W (Steps 42 and 43).

    H1'=g1'(h1,L', SH1, SH2,SH3,SW1,SW2,SW3)                   (10)

    W'=g3'(w1,L'SH1,SH2,SH3,SW1,SW2,SW3)                       (11)

Functions g1' and g3' may be experimentally determined or,alternatively, may be theoretically determined.

For measurement at the second wavelength (Step 44), the replacement ofthe space filter, the pickup of a scatter image, the extraction of ascatter profile, the computation of scatter parameters SH1' to SH3' andSW1' to SW2' are carried out (Step 45), and then the peak height h2 inthe equation (4) is corrected as follows for determination of acorrected peak height H2' (Steps 44 and 45).

    H2'=g2'(h2,L',SH1',SH1',SH2',SH3',SW1',SW2',SW3')          (12)

A function g2' is determined in the same manner as the function g1'.Then, the routine returns to Step 13a in FIG. 13. The hemoglobinconcentration HGB and the hematocrit HCT are determined on the basis ofH1', H2' and W' (Step 13a).

Embodiment 3

The blood analyzers described in Embodiments 1 and 2 are a bloodanalyzer of transmitted light type in which the concentration of a bloodconstituent is computed on the basis of a transmitted light image. Onthe other hand, Embodiment 3 employs a blood analyzer of reflected lighttype in which the concentration of a blood constituent is computed onthe basis of a reflected light image.

While the measurement site for the blood analyzer of transmitted lighttype is limited to fingers and earlobes through which the light can betransmitted, the blood analyzer of reflected light type is advantageousin that it can be applied to a wide range of bodily portions such as asole, a cheek, and an abdomen. Therefore, the blood analyzer ofreflected light type is effective on subjects such as an infant and ababy whose fingers cannot be easily fixed and held.

Also, a reflected light employed in this Embodiment can be in a shorterwavelength range, namely, 400 nm to 950 nm. Since the light having ashorter wavelength is absorbed by hemoglobin to a greater extent, it ispossible to perform a more accurate measurement.

There will next be described the construction of the blood analyzeraccording to Embodiment 3 of the present invention. FIG. 21 is asectional view showing a structure of a detecting section 1b accordingto Embodiment 3 of the present invention. FIG. 22 is a bottom view ofthe detecting section 1b. Here, the blood analyzer of Embodiment 3 isthe same as the blood analyzer of Embodiment 1 except that the detectingsection is modified and, therefore, an explanation of the other elementsis omitted.

As shown in FIGS. 21 and 22, the detection section 1b is compactlyconstructed by incorporating an image pickup device 15a and a lens 14bdisposed in a central portion of a tubular housing 41, and by disposingLEDs 11c and 11d in the periphery thereof as a light source. The lightsource may include laser diodes or may be introduced from outside byemploying a ring fiber. If a larger quantity of light is required in theblood analyzer of reflected light type than in the blood analyzer oftransmitted light type, the number of the light sources, i.e., LEDs 11cand 11d can be increased to meet the requirement in this Embodiment.

A bell-like rubber seat 42 is provided in the periphery of the housing41 for stably holding the detecting section 1b on a bodily portion 16a.Here, the LEDs 11c and 11d emit lights of different wavelengths, whichcorrespond to the first and second wavelengths in Embodiment 1. Imagesobtained from the detecting section 1b are processed in the manneralready explained in Embodiment 1.

INDUSTRIAL APPLICABILITY

The industrial applicability of the present invention is as follows:

(1) A transcutaneous blood analysis can be realized without employingthe avascularization method or the sphygmic spectrometry;

(2) A transcutaneous and noninvasive determination of the hemoglobinconcentration and the hematocrit can be realized with a simpleconstruction;

(3) Since a particular measuring object (a particular blood vessel ofinterest) can be defined, results can be obtained with an improvedreproducibility;

(4) The hemoglobin concentration and the hematocrit can continuously bemonitored;

(5) Results can be obtained with an improved reproducibility by way ofimage processing;

(6) A blood analyzer having a reduced size can be realized at a lowcost; and

(7) The blood analyzer can be used as an anemia checker.

What is claimed is:
 1. A noninvasive blood analyzer comprising:a lightsource for illuminating part of a tissue of a living body including ablood vessel; an image pickup section for picking up an image of theilluminated blood vessel and tissue; and an analyzing section foranalyzing the image, wherein the analyzing section includes; anextracting section for extracting an image density distribution acrossthe blood vessel in the image as an image density profile; a quantifyingsection for quantifying configurational characteristics of the imagedensity profile; a computing section for computing an amount of a bloodconstituent on the basis of the quantified characteristics; and anoutputting section for outputting the computed amount.
 2. A noninvasiveblood analyzer as set forth in claim 1, wherein the amount of the bloodconstituent is at least one of hemoglobin concentration and hematocrit.3. A noninvasive blood analyzer as set forth in claim 2, wherein theimage pickup section includes an object lens, a focusing lens, a spacefilter disposed between the lenses and having two-dimensionally variabletransmittances, and filter controlling means for two-dimensionallyvarying the transmittance of the space filter.
 4. A noninvasive bloodanalyzer as set forth in claim 3, wherein the image pickup sectionfurther includes adjusting means for adjusting the position of a focalpoint of the object lens with respect to the blood vessel.
 5. Anoninvasive blood analyzer as set forth in claim 4, wherein thequantifying section normalizes the image density profile, and computes apeak value h and a distribution width w corresponding to the diameter ofthe blood vessel from the normalized image density profile.
 6. Anoninvasive blood analyzer as set forth in claim 5, wherein thequantifying section computes a depth L defined between a surface of thebody tissues and the blood vessel on the basis of the position of thefocal point of the object lens which is adjusted by the adjusting meanssuch that the sharpest image is picked up, and corrects the peak value hand the distribution width w on the basis of the depth L.
 7. Anoninvasive blood analyzer as set forth in claim 3, wherein thequantifying section normalizes the image density profile, and computes apeak value h and a distribution width w corresponding to the diameter ofthe blood vessel from the normalized image density profile.
 8. Anoninvasive blood analyzer as set forth in claim 7, wherein thequantifying section corrects the peak value h and the distribution widthw on the basis of a plurality of images picked up every time thetransmittance of the space filter is two-dimensionally varied.
 9. Anoninvasive blood analyzer as set forth in claim 1, wherein the lightsource comprises a light emitting device which is adapted to selectivelyemit light beams of first and second wavelengths, which aresubstantially isosbestic for oxidized and reduced hemoglobins.
 10. Anoninvasive blood analyzer as set forth in claim 1, wherein theextracting section searches for an area in the image where a bloodvessel image stands in the sharpest contrast and extracts the imagedensity profile from the area thus searched for.
 11. A noninvasive bloodanalyzer as set forth in claim 1, wherein the quantifying sectionnormalizes the image density profile, and computes a peak value h and adistribution width w corresponding to the diameter of the blood vesselfrom the normalized image density profile.
 12. A noninvasive bloodanalyzer as set forth in claim 11,wherein the light source comprises alight emitting device which is adapted to selectively emit light beamsof first and second wavelengths; wherein the quantifying sectioncomputes peak values h1 and h2 and distribution widths w1 and w2 offirst and second profiles respectively obtained by picking up images ofthe same part of the body tissues at the first and second wavelengths;and wherein the computing section computes the concentration ofhemoglobin and hematocrit on the basis of the computed peak values h1and h2 and distribution widths w1 and w2.
 13. A noninvasive bloodanalyzer as set forth in claim 12, wherein the quantifying sectionestimates a depth L at which the blood vessel is located on the basis ofthe distribution widths w1 and w2 of the first and second image densityprofiles obtained by picking up images of the same part of the bodytissues at the first and second wavelengths, and corrects the peakvalues h1 and h2 on the basis of the depth L.
 14. A noninvasive bloodanalyzer as set forth in claim 1, further comprising a fixing member forrelatively fixing the living body to the light source and the imagepickup section.
 15. A noninvasive blood analyzer as set forth in claim1, wherein the image pick up section picks up a transmitted light imageof the blood vessel and the tissue.
 16. A noninvasive blood analyzer asset forth in claim 1, wherein the image pick up section picks up areflected light image of the blood vessel and the tissue.
 17. Anoninvasive blood analyzer comprising:a light source for illuminatingpart of a tissue of a living body including a blood vessel; an imagepickup section for picking up an image of the illuminated blood vesseland the tissue; and an analyzing section for analyzing the image, theanalyzing section analyzing an image of the blood vessel in the image tocompute an amount of a blood constituent and output a computationresult; wherein the light source comprises a light emitting device whichis adapted to selectively emit light beams of first and secondwavelengths, which are within a range between 600 and 950 nm.
 18. Anoninvasive blood analyzer as set forth in claim 17, wherein the amountof the blood constituent is at least one of hemoglobin concentration andhematocrit.
 19. A noninvasive blood analyzer as set forth in claim 17,further comprising a fixing member for relatively fixing the living bodyto the light source and the image pickup section.
 20. A noninvasiveblood analyzer as set forth in claim 17, wherein the image pickupsection-picks up a transmitted light image of the blood vessel and thetissue.
 21. A noninvasive blood analyzer as set forth in claim 17,wherein the image pickup section picks up a reflected light image of theblood vessel and the tissue.
 22. A noninvasive blood analyzercomprising:a light source for illuminating part of a tissue of a livingbody including a blood vessel; an image pickup section for picking up animage of the illuminated blood vessel and the tissue; and an analyzingsection for analyzing the image, the analyzing section analyzing animage of the blood vessel in the image to compute an amount of a bloodconstituent and output a computation result; wherein the image pickupsection includes an object lens, a focusing lens, a space filterdisposed between the lenses and having two-dimensionally variabletransmittances, and filter controlling means for two-dimensionallyvarying the transmittance of the space filter.
 23. A noninvasive bloodanalyzer as set forth in claim 22, wherein the image pickup sectionfurther includes adjusting means for adjusting the position of a focalpoint of the object lens with respect to the blood vessel.